European Offenlegungsschrift 0 337 826 describes a sensor matrix in which the first electrodes of the sensors are interconnected in a first direction, for example in the row direction, the second electrodes being interconnected in a direction extending at an angle of 90.degree. with respect to the first direction, for example in the column direction. Between the two electrodes there are several, stacked semiconductor layers. The X-ray sensitivity of this sensor matrix is achieved in that a luminescent layer is provided on the outer electrode, which luminescent layer emits light when X-rays are incident, the light producing the desired reaction in the semiconductor layers. X-rays are thus indirectly measured by means of the luminescent layer.